Switching java verison was a bit annoying, so I made it a bash function so that it can be used like a command.

reference: http://shinsuke789.hatenablog.jp/entry/2017/08/16/103000 https://qiita.com/ponsuke0531/items/795cd00d93b71c14d07b

bash additions

Edit ~ / .bash_profile

$vi ~/.bash_profile

Add the following

`~/.bash_profile`


#!/bin/bash

#PATH initialization
export PATH=/sbin:/bin:/usr/bin:/usr/local/bin:/usr/sbin

#~~~usually~/.bash_Processing done in profile~~~
# ~/.use-java-version
if [ -f ~/.use-java-version ]; then
        export JAVA_HOME=$(cat ~/.use-java-version)
else
        #I default to java8
        /usr/libexec/java_home -v 1.8 | tee ~/.use-java-version
        export JAVA_HOME=$(cat ~/.use-java-version)
fi
export PATH=$JAVA_HOME/bin:$PATH

function lsjava () {
        #Output installed java
        echo -e "\033[0;33mInstalled java version:\033[0;39m"
        /usr/libexec/java_home -V
        #Output java currently in use
        echo -e "\n\033[0;33mCurrent specificed java version:\033[0;39m"
        java -version
}
function chjava () {
        #If no parameters are specified
        if [ -z "$1" ]; then
                echo -e "Please specific java version. \nex)\n\$ chjava 1.8"
                return 1
        fi
        /usr/libexec/java_home -v $1
        local checkJavaVersion=$?
        #If the specified java version is not installed
        if [ $checkJavaVersion -ne 0 ]; then
                echo "Please specific installed java version."
                echo Java $1 is not installed.
                return 2
        fi
        echo Use java $1.
        /usr/libexec/java_home -v $1 | tee ~/.use-java-version
        # ~/.use-java-Since the java path used for version is output, the upper if[ -f ~/.use-java-version ]By the way, it will be added to the PATH
        source ~/.bash_profile
        #Show PATH
        echo PATH=$PATH
　　　　　　　　　　　　　　　　#Show java version in use
        java -version
        return 0
}

Load the modified bash_profile.

`python`


$source ~/.bash_profile

function

java version switching

Do it with $ chjava [java version]

#Specify java10
$chjava 10.0

#Specify java8
$chjava 1.8

Error handling

#If you forget the parameters
$chjava
Please specific java version.
ex)
$ chjava 1.8

#If a java version that is not installed is specified
$chjava 1.9
Unable to find any JVMs matching version "1.9".
/Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home
Please specific installed java version.
Java 1.9 is not installed.

Currently installed java version & version in use

Do it with $ lsjava

$lsjava
Installed java version:
Matching Java Virtual Machines (3):
    10.0.1, x86_64:	"Java SE 10.0.1"	/Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home
    1.8.0_121, x86_64:	"Java SE 8"	/Library/Java/JavaVirtualMachines/jdk1.8.0_121.jdk/Contents/Home
    1.8.0_101, x86_64:	"Java SE 8"	/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home

/Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home

Current specificed java version:
java version "1.8.0_121"
Java(TM) SE Runtime Environment (build 1.8.0_121-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.121-b13, mixed mode)

Simplify java version switching (Mac)